Zoj 2100 Seeding

<pre class="html" name="code">#include<stdio.h>   char map[8][8];  int visited,flag;  int n,i,j,m;  void dfs(int x,int y)  {      if( x<0 || y<0 || x>=n || y>=m)         return;     if(map[x][y]!='.')          return;     if(flag)         return;     map[x][y] = 's';      visited++;     if(visited == n*m)    {         flag=1;         return;     }      dfs(x+1,y);     dfs(x-1,y);      dfs(x,y+1);      dfs(x,y-1);      visited--;     map[x][y]='.'; }    int main(void)  {      while(scanf("%d%d",&n,&m) && n && m)      {          for(i=0;i<n;i++)              scanf("%s",map[i]);                    for(i = 0 , visited = 0 ; i < n ; i++)              for(j = 0;j<m;j++)                  if(map[i][j]=='S')                       visited++;                    flag = 0;          dfs(0,0);          if(flag) printf("YES\n");          else printf("NO\n");               }        return 0;  }